U.S. patent number 7,289,639 [Application Number 10/502,367] was granted by the patent office on 2007-10-30 for hearing implant.
This patent grant is currently assigned to Sentient Medical Ltd. Invention is credited to Eric Abel, Robert Mills, Zhigang Wang.
United States Patent |
7,289,639 |
Abel , et al. |
October 30, 2007 |
Hearing implant
Abstract
The present invention relates to a hearing aid system comprising
a hearing implant and a method of powering a hearing implant, the
system comprising an external ear canal module and an implant,
wherein the signalling and/or powering of the ear implant is by way
of a light signal being provided to the implant through the ear
drum from, for example, the ear canal module.
Inventors: |
Abel; Eric (Dundee,
GB), Wang; Zhigang (Dundee, GB), Mills;
Robert (Edinburgh, GB) |
Assignee: |
Sentient Medical Ltd
(GB)
|
Family
ID: |
9929642 |
Appl.
No.: |
10/502,367 |
Filed: |
January 24, 2003 |
PCT
Filed: |
January 24, 2003 |
PCT No.: |
PCT/GB03/00264 |
371(c)(1),(2),(4) Date: |
March 02, 2005 |
PCT
Pub. No.: |
WO03/063542 |
PCT
Pub. Date: |
July 31, 2003 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20050163333 A1 |
Jul 28, 2005 |
|
Foreign Application Priority Data
|
|
|
|
|
Jan 24, 2002 [GB] |
|
|
0201574.1 |
|
Current U.S.
Class: |
381/312;
381/326 |
Current CPC
Class: |
H04R
23/008 (20130101); H04R 25/606 (20130101); H04R
2225/023 (20130101); H04R 2225/67 (20130101) |
Current International
Class: |
H04R
25/00 (20060101) |
Field of
Search: |
;381/312,314,315,322,323,326,328,380,190 ;600/25 ;607/55,56,57 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
28 44 979 |
|
Apr 1980 |
|
DE |
|
35 08 830 |
|
Sep 1986 |
|
DE |
|
60154800 |
|
Aug 1985 |
|
JP |
|
WO 97/32385 |
|
Sep 1997 |
|
WO |
|
WO 00/76271 |
|
Dec 2000 |
|
WO |
|
Other References
Leirner AA, Oshiro MS, Nunes CA, Bento Ref, Miniti A. (ENT Dept.,
Medical School, University of Sao Paolo, Brazil) "A pathway for
information transmission to the inner ear. Application to cochlear
implants." Asaio J. Jul.-Sep. 1992; 38(3):M253-6. cited by
other.
|
Primary Examiner: Le; Huyen
Attorney, Agent or Firm: Gifford Krass Sprinkle Anderson
& Citkowski
Claims
The invention claimed is:
1. A hearing aid system comprising: an ear canal module for
location in the ear canal of a user, the ear canal module
comprising a microphone for converting sound into an electrical
signal and a light source for converting said electrical signal
into a light signal and for transmitting said light signal to the
middle or inner ear of the user; and an implant for location in the
middle or inner ear of a user, the implant comprising a
photoreceiver and a hearing actuator, the photoreceiver being
operative to detect the light signal transmitted from the ear canal
module and convert said light signal into a further electrical
signal for driving the hearing actuator; wherein, in use, light
signals transmitted from the ear canal module constitute the sole
input to the implant.
2. The hearing aid system according to claim 1 wherein the ear
canal module comprises a further light source for transmitting a
further light signal for charging a battery within the implant, the
battery serving to provide additional power to the implant.
3. The hearing aid system according to claim 1 wherein the
components of the microphone and the light source are contained
within a single housing which is shaped to fit within the ear canal
of the user.
4. The hearing aid system according to claim 1 wherein the light
source is a light emitting diode (LED).
5. The hearing aid system according to claim 1 wherein the light
signal is near infrared (NIR) light or infrared (IR) energy.
6. The hearing aid system according to claim 1 wherein a channel or
a valve is provided in the module so as to provide a passage
through the module thereby preventing blockage of the ear
canal.
7. The hearing aid system according to claim 1 wherein the implant
is an integrated photoreceiver/actuator unit.
8. The hearing aid system according to claim 7 wherein the
integrated photoreceiver actuator unit is a micro electromechanical
system (MEMS)-integrated photoreceiver/actuator.
9. The hearing aid system according to claim 1 wherein the
photoreceiver is a photo-sensitive diode or photovoltaic cell.
10. The hearing aid system according to claim 1 wherein the hearing
actuator is arranged in use to contact the ossicular chain.
11. The hearing aid system according to claim 10 wherein the
hearing actuator is located on the incus long process, the
incodostapedial joint or the stapes.
12. The hearing aid system according to claim 10 wherein the
actuator is arranged in use to be positioned in the middle ear.
13. The hearing aid system according to claim 10 wherein the
hearing actuator is secured in place by cementing, grafting or by
mechanical means.
14. The hearing aid system according to claim 1 wherein actuation
of the middle or inner ear compounds is by mechanical or electrical
means.
15. The hearing aid system according to claim 14 wherein actuation
is by mechanical means, wherein the actuator is in the form of a
thin disk or disk made of piezo ceramic material.
16. The hearing aid system according to claim 15 wherein the piezo
ceramic material is lead zirconate titanate (PZT) or PLZT.
17. The hearing aid system according to claim 14 wherein actuation
is by mechanical means, wherein the hearing actuator comprises a
flexible diaphragm.
Description
FIELD OF THE INVENTION
The present invention relates to a hearing aid system comprising a
hearing implant and method of powering a hearing implant.
BACKGROUND OF THE INVENTION
Sensorineural deafness is by far the most common type of hearing
loss. Deafness affects 9 million people in the United Kingdom, of
which about 95% have sensorineural deafness (source Defeating
Deafness, United Kingdom). Causes include congenital, bacterial,
high intensity noise and, especially, the ageing process, with 30
percent of those affected being over 60 years. Hearing impairment
is the third most common chronic problem affecting the ageing
population--and one of the least diagnosed. There is also an
increased prevalence in some sections of the younger age group, due
to exposure to loud noise.
There are currently no effective means of repairing the cochlea or
the nervous pathways to the brain. For most patients, hearing can
be restored adequately by sufficient amplification of sound with a
hearing aid. Hearing aids have a number of problems: acoustic
feedback (because the microphone is very close to the speaker),
inadequate sound quality, and discomfort due to occlusion of the
ear canal. They also are undesirable from the social point of view,
in that the appearance of wearing a hearing aid can cause users to
feel that they are seen to be handicapped. The alternative is an
implantable device.
Middle ear implants provide mechanical amplification by vibrating
the ossicular chain. They are intended for patients with moderate
to severe sensorineural hearing loss, who still have residual
hearing. They could potentially benefit up to 50% of all people
with hearing loss. Cochlear implants, the alternative, provide
electrical stimulation to the nerves of the inner ear, but are
suitable only for the profoundly deaf, as all residual hearing is
destroyed during their implantation. They are not favoured where
there are alternative solutions.
Middle or inner ear implants however require a power supply. A few
use incorporated batteries, which although last several years,
require replacement. This undesirably necessitates a further
operation for the patient. Other implants use wires through the
skull and the rest use radiofrequency or inductively coupled
methods. Nevertheless, radio frequency modulated transmission uses
complicated circuitry, is cumbersome and costly, and the implanted
receiver module itself has a heavy demand on power. It also has to
be approved under each country's radiofrequency regulations.
Inductively coupled transmission methods use two coils or one coil
and one magnet separated in close proximity. However, problems
include high power consumption, signal variations and background
noise. Moreover, MRI compatibility can also be a problem with some
components.
It is an object of the present invention to obviate and/or mitigate
at least one of the aforementioned disadvantages and/or
problems.
SUMMARY OF THE INVENTION
Broadly speaking the present invention is based on powering a
middle or inner ear implant using a light signal.
In a first aspect the present invention provides a hearing aid
system comprising an external ear canal module and an implant;
the external ear canal module comprising a microphone, a light
source, a power source and necessary electronic circuitry;
the implant comprising a photoreceiver actively coupled to a
hearing actuator; and
wherein in use, sound detected by the microphone of the external
ear canal module is converted and transmitted by the light source
as a modulated light signal, the modulated light signal being
detected by the photoreceiver of the ear implant and converted to
an electrical signal for driving the hearing actuator.
The implant it will be understood is located within the middle or
inner ear, i.e the body side of the ear drum.
Advantageously the present system is such that the light signal may
be sufficient to not only provide the sound information, but also
power the ear implant. In this manner, the ear implant need not
have its own internal power source. Alternatively or additionally a
further light source may be used to charge a battery within the ear
implant so as to provide additional power to the implant.
Thus, in a further aspect, the present invention provides a method
of powering and/or signalling an ear implant comprising
transmitting a light source, or sources through a patients ear
drum, such that said light source(s) is/are received by the ear
implant and wherein said light source(s) is/are capable of powering
and/or signalling the ear implant.
The components of the external ear canal module are typically
contained within a single housing which is shaped to fit within the
external ear canal. The microphone is positioned within the housing
such that in use it can easily detect sounds. Thus, the microphone
is generally arranged to be directed towards the outside of the ear
for receiving sound. The sound received by the microphone is
transduced by appropriate means known to those skilled in the art,
into an electrical signal which in turn is converted into a
modulated signal by suitable modulating means. The modulated signal
is then output as a modulated light signal from the light
source.
The light source may be for example a light emitting diode (LED)
and the light signal itself may be visible light or preferably near
infrared (NIR) light or infrared (IR) energy. Studies have shown
that IR light can penetrate over 15 mm of tissue at frequencies up
to 30 KHz. The light which is output by the module is to be
received by the middle-ear implant. Thus, the light source is
arranged in use so as to emit the light in the direction of the
photoreceiver. The light source therefore emits the light towards
and through the ear drum for detection by the photoreceiver.
The skilled addressee is well aware of the electrical circuitry
required for the module and a power source, typically a battery,
rechargeable or otherwise, is required to power the components of
the module.
Although generally designed to fit snugly within the external ear
canal so as to not easily fall out, the module should conveniently
not completely occlude the ear canal. In this manner a channel,
valve or the like may be provided in the module so as to provide a
passage through the module thereby preventing blockage of the ear
canal. It is understood that such a channel valve or the like could
be associated with the housing of the module and, for example, a
channel could be cut into the external surface of the module.
The implant may be an integrated photoreceiver/actuator unit such
as a micro electromechanical system (MEMS)-integrated
photoreceiver/actuator. The photoreceiver/actuator may be a single
unit, or the photoreceiver and actuator may be separate and
electrically connected by wiring. The photoreceiver may be a
photo-sensitive diode, photo voltaic cell or other type of
photoreceiver which may be located anywhere in the middle ear,
providing it can receive light generated from the light source of
the ear canal module. It may be covered by a biocompatible coating,
which could include coverage of the photoreceiver.
In order that a patient suffers no or minimal residual hearing
loss, the implant may sit on the ossicular chain, rather than
linking to it from a remote fixation, such that the only additional
mechanical impedance is due to the small mass of the actuator
itself. Locating the actuator on the ossicular chain may also help
to eliminate any post-operative alterations to implant performance
from tightening or loosening of the actuator-ossicle coupling
during the healing of swollen tissues, and from small displacements
arising from the altered gravitational effects of lying down during
the operation and sitting/standing up afterwards.
The actuator may, for example, be located on the incus long
process, the incudostapedial joint (which could be disarticulated
temporarily without damage for the fitting of an annular shaped
actuator) or the stapes. The actual design of the actuator will be
determined by the skilled addressee according to the location
selected, an important aim being to reduce acoustic feedback An
alternative position may be in the inner ear, for example the
promontory, where coupling may be direct, via fenestration: a
surgical technique to create a window in the inner ear in order to
contact the inner ear fluid directly, or using an external
anchoring support.
The actuator may be secured in place by methods such as cementing,
grafting or mechanical means, for example screws or barbs. It could
be osseointegrated with the ossicular chain.
Actuation may be mechanically driven or electrical. In the middle
ear, actuation will generally be mechanical vibration of the
ossicular chain, or more specifically individual bones thereof. If
the actuator is placed in the inner ear, actuation may be carried
out mechanically by for example direct or indirect vibration of the
perilymph fluid in the inner ear, or electrically to an electrode
or electrode array, coupled for example to the cochlea.
In order to drive a mechanically operated actuator, light is
received by the photoreceiver, which is in turn converted into an
electrical output which drives the actuator resulting in
vibrations. Typically the actuator may be a thin disk made of piezo
ceramic material such as lead zirconate titanate (PZT), or lead
lanthanum zirconate tibanate PLZT. This is desirable because the
materials are magnetic resonance imaging (MRI) compatible, as well
as being efficient transducers. Additionally more than one disk may
be provided in a desired configuration and/or disk may be more than
one layer thick. The vibrations may also be generated using for
example a disk(s) of piezo ceramic in conjunction with a flexible
diaphragm of for example stainless steel, titanium, or
aluminium.
Furthermore, the use of a flexible diaphragm permits hydraulic
amplification to increase the displacement of the flexible
diaphragm. For example, an increase in the displacement of the
flexible diaphragm can be obtained using a simple fluid-filled tube
coupled to a larger diameter disk actuator which is located at the
opposite end of the tube from the flexible diaphragm and may
contact for example the perilymph. Such a tube structure allows the
actuator module to be placed in the middle ear cavity which
provides more space for accommodation and support.
BRIEF DESCRIPTION OF THE DRAWINGS
As an example, a PZT disc actuator now in use in an incus-driven
middle ear implant operates at 1V and 100 .mu.A. This power
requirement could be generated from the photodetector without the
need for further electronic amplification. Passive RC filtering
could be used for demodulation. In case a higher voltage or current
is needed to drive the actuator, a simple op-amp would be
sufficient which will consume very little extra power other than to
drive the actuator. The additional power could come from another
modulated source or a DC frequency in the light signal.
An embodiment of the present invention will now be described in
more detail and with reference to the following FIG.:
FIG. 1 shows the possible locations of an ear canal module and ear
implant according to the present invention;
FIG. 2 shows a block diagram identifying the components of the ear
canal module and ear implant of the present invention;
FIG. 3 is a schematic depiction of a testing system used to
evaluate the present invention; and
FIG. 4 is a graphic depiction of displacement versus frequency as
measured using the test apparatus of FIG. 3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows somewhat schematically the relative locations of the
external ear canal module 1 and ear implant 20. As can be seen, the
ear module 1 is located in the ear canal 3. The ear module 1 has a
channel 5 through the module 1 in order to prevent occlusion of the
ear canal 3. A modulated IR light signal, represented by the dashed
lines 7, is emitted by an LED 9, through the ear drum 12, so as to
be detected by an implant 20. In this embodiment, the implant 20
sits on the incudostapedial joint, so as to oscillate the stapes,
although the implant could be located elsewhere, for example in the
promontory.
FIG. 2 shows in more detail the components of the ear module 1 and
implant 20 of the present invention. The ear module 1 comprises a
microphone 11, and associated electronic circuiting 13 for
transducing sound into an electrical signal which is in turn
converted and transmitted as the modulated light signal 7 (shown as
broken arrows) by the LED 9. Power for the ear module is provided
by a battery 15. The modulated light signal 7 passes through the
ear drum 12 and is detected by a photodiode 22 of implant 20. The
photodiode 22 converts the light signal 7 into an electrical signal
for driving/oscillating a disk actuator 24 made of PZT piezo
ceramic material.
Advantageously the hearing system features surgical simplicity,
safety and life-long durability (no implanted battery needs to be
replaced), easy updating of signal processing (external module)
algorithms, minimum or no deterioration (destruction) of the
residual hearing level, minimum or no acoustic feedback and canal
occlusion problems which are inherent with conventional hearing
aids, low-cost and acceptability for both the surgeons and the
patients.
To illustrate the efficacy of the present invention, the inventors
have tested the feasibility of two components of the invention ie.
the ossicular mounted piezoelectric actuator and the infrared
telemetry system.
We have tested the feasibility of the two key innovations in this
project, i.e. the ossicular mounted piezoelectric actuator and the
infrared telemetry system.
(a) Ossicular mounted piezoelectric actuator. An ossicular mounted
actuator is used in the Soundbridge implant [1], but it has an
electromagnetic actuator with a moving mass component, so the
vibrating mechanism is not directly comparable with the presently
proposed design. The piezoelectric actuator used for the pilot
study was an 8 mm diameter single layer disk bender, of the type
used in the TICA hearing implant (2). The output vibration level of
the TICA actuator is well documented and has been shown clinically
to satisfy the requirements of a hearing implant [2]. This makes it
suitable for demonstrating the ossicular mounted concept. The
actuator is available commercially (American Piezo Company). Its
total thickness is 0.22 mm and its mass is less than 150 mg.
FIG. 3 shows a schematic of the test configuration, which was
designed to be a more demanding load than the real ossicular chain.
A copper wire was used to simulate the ossicular chain. It was
glued at one end to a 17 mm long section of flexible plastic
sleeving (polyolefin, 12.7 mm bore, 0.3 mm thick, weight 0.36 g),
giving a crude representation of the eardrum. The wire weighed 60
mg, which is about 10% heavier than the ossicular chain [3]. The
other side of the tube was glued to a solid framework. The wire
passed through the centre of the actuator, with a tight fit to hold
it in place. The protruding wire weighed about 8 mg, twice the
weight of the stapes. Reference data were obtained for an unloaded
actuator, which was attached around its circumference to a solid
framework, FIG. 3(b). Vibration was measured with a laser
vibrometer. FIG. 4 shows the measured displacements.
The TICA is reported as producing 22 nm at 2.83V peak to peak [2],
which was found to be equivalent to around 100 dB SPL at 1 kHz and
more than 130 dB SPL (Sound Pressure Level) at higher frequencies
[2]. The `ossicular mounted` actuator of the present invention gave
a nearly flat response of 47 nm below 4 kHz at 1V excitation,
considerably higher than the TICA, and a similar resonant frequency
of 7-10 kHz.
(b) Infrared light transmission. Light transmission was tested
through a chicken skin, which is more opaque than the eardrum and
at least twice as thick. The simulation was otherwise as realistic
as possible, in terms of the likely size of the light emitting
diode (LED) source and the distances for the light path. The energy
detected by a photodiode was used to drive the disk bender actuator
and could produce a vibration displacement level equivalent to 100
dB SPL, which is more than adequate for an implant, using 2.1 mW
optical power. A custom made actuator is envisaged to perform much
better. The level of infrared energy used was less than 1% of the
level that could cause tissue damage, according to British Standard
EN 60825-1: 1994 Safety of Laser Products. This demonstrates the
viability of the trans-eardrum telemetry concept.
REFERENCES
[1] Lenarz T, Weber B P, Mack K F, Battmer R D, Gnadeberg D. The
Vibrant Soundbridge System: a new kind of hearing aid for
sensorineural hearing loss. 1: Function and initial clinical
experiences. Laryngorhinootologie. 1998; 77: 247-55. (In
German).
[2] Zenner H P, Leysieffer H, Maassen M, et al. Human Studies of a
Piezoelectric Transducer and a Microphone for a Totally Implantable
Electronic Hearing Device. American Journal of Otology, 2000; 21:
196-204.
[3] Kirkae I. The structure and function of the middle ear.
University of Tokyo Press, Tokyo, 1960.
* * * * *